[maemo-developers] Maemo-mapper vector data backend follow-up

[From: Simon Pickering]

Hi Till, 

> do you want an honest reply: Don't do that. Maemo-Mapper 
> isn't meant to handle
> vector data. Period.

Indeed, but maemo-mapper will not be handling the vector data, that will be
the job of the render/routing server; maemo-mapper will continue handling
bitmap data.

> These are my concerns:
> 
> - Plenty of duplicate data will get stored that isn't 
> required since Maemo-Mapper 
>   will locally cache tiles that have been generated on the 
> device itself.

This can be disabled - only a memory cache is used, no file cache; though it
might be useful to cache the tiles to a file cache and clear that when the
app closes to avoid unnecessary processing when panning. I don't know.

> - Rendering is less than optimal because Maemo-Mapper asks 
> for tiles. You'd 
>   have to a) render most things several times as most objects 
> will span several 
>   tiles and b) have to render more data than required as 
> Maemo-Mapper does
>   some caching in advance.

True, this then boils down to how fast the rending can be performed and with
what CPU load.

> - You'd need massive interfaces between your renderer and 
> Maemo-Mapper for
>   all kinds of interaction with the maps. You'd e.g. have to 
> communicate
>   POI details, street details, etc etc ...

Well the only interfaces that are really required are ways of sending
rendered tiles, and sending GPX routes from A to B, and lookups of the
lat/long of POI locations/street locations, etc.

> - The entire thing will not be trivial to use and debug as 
> you are basically
>   planning to cut an already complex navi application into 
> two parts which
>   then need proper coupling.

I'm sure it won't be trivial, but the rendering engine and routing engines
should be pretty well self contained, I can't see why it should be any more
difficult than it appears at first glance.

> - All navigation functionality of Maemo-Mapper is imho done 
> on an external
>   server in advance. You'd also have to port a navigation 
> engine onto maemo
>   and couple it with maemo-mapper as well as with your tile renderer.

Indeed, this is the idea.

> I'd rather use software that was designed to use vector data. 
> E.g. navit has
> been ported to maemo by a bunch of people incl. myself. We 
> all didn't put
> much effort into this and the results are barely useable. But 
> it's imho way
> more effective with respect to vector data to continue with a 
> program like 
> navit than Maemo-Mapper.

You are probably right there (certainly things like 3D views are outside the
scope of maemo-mapper), but there is a desire to support local vector-data
backends, and this is a discussion of whether it can be done.

I fully support the work on Navit and other navigation/mapping programmes,
this is simply looking at an expansion of the abilities of maemo-mapper.

> Regards,
>   Till

Cheers,

Simon